We will take resistance measurements on the +V and -V supply.
Set your DMM to 20KΩ range.

To check the +V supply, connect BLACK probe to J401, RED probe to J403.
(You may have to lift R505, but let's see how it goes.)

[To check the -V supply, connect RED probe to J402, BLACK probe to J401.]

Correction:
To check the -V supply, connect RED probe to J401, BLACK probe to J402.


Install

IC402
Q416
Q426
Q430

Edit: wrong connection now corrected.

 

Install

IC402
Q416
Q426
Q430

By this you mean.. install a new Q416 and a new Q426 ? Because they did not measure ok?

 

That is the correct assumption. Install new ... if originals are bad.

 

I would have hoped that someone spotted my error in post #241 which I have now corrected.

 

OK, let's see..
I see you have corrected.

Measured resistance,put DMM to 20K range:

Black to J401 and Red to J403: 14,17Ω
Then i lifted one leg of R505, and measured again: It got out of range.. open.

Red to J401 and Black to J402: Out of range... open

I actually got one thing wrong in post #242, Q426 tested OK earlier. But i did manage to drop it and i don't know were it went so i installed a new.

Installed:

New Q416
New Q426
Q430
IC402

I have many of IC402.. should i install a new one (?)

 

Sure, it would not hurt to insert a new IC402.

 

Sure, it would not hurt to insert a new IC402.

Ok. Then i will do that.

After that? Is it power on?

 

Install new
Q401
Q405

We cannot do a power test until we get replacements for R505, R506, 6.8Ω ¼W resistors

 

Install new
Q401
Q405

We cannot do a power test until we get replacements for R505, R506, 6.8Ω ¼W resistors

Ok i will install

I forgot to mention, i have got hold of two replacements 6.8Ω ¼W

 

Marius, I think the plan is to work our way back till you get all the components reinstalled ... the resistance tests at each stage of the game prior to the application of power. But I will let Mr Chips confirm that.

 

Black to J401 and Red to J403: 14,17Ω
Then i lifted one leg of R505, and measured again: It got out of range.. open.

That is 14.17 ohms or 14.17 kohms as you were on the 20 kohm scale? I don't want to be confused.

 

That is 14.17 ohms or 14.17 kohms as you were on the 20 kohm scale? I don't want to be confused.

My guess is that he meant 14.17kΩ.

 

Marius, I think the plan is to work our way back till you get all the components reinstalled ... the resistance tests at each stage of the game prior to the application of power. But I will let Mr Chips confirm that.

Correct. We will do resistance tests:
RED to J403, BLACK to J401
RED to J401, BLACK to J402

Next step is resolder R505 and install new R506.

Power up.
Measure voltage at
TP401 - 1
TP401 - 2
TP401 - 3
TP401 - 4

TP501 - 1
TP501 - 2

TP502 - 1
TP502 - 2

 

My guess is that he meant 14.17kΩ.

I too have that hope. If it were the former, it would be best not to apply power. In fact the opposite power supply rail should read the same using the opposite or reverse connection. I don't think anyone wants to replicate the work already done.

MrChips, I only broke from our conversation mode because of the confusion and what would happen if it were the former (14.xx) vice the latter (14.xx k).

 

That is 14.17 ohms or 14.17 kohms as you were on the 20 kohm scale? I don't want to be confused.

Yes JoeJester, i were on the 20K scale, so that would be 14,17 kΩ Sorry for giving confusing answers

 

Correct. We will do resistance tests:
RED to J403, BLACK to J401
RED to J401, BLACK to J402

Next step is resolder R505 and install new R506.

I understand

So i will now install

new IC402
Q401
Q405
new R506
resolder R505

And then power up, check for smoke and measure the voltages you listed.. ok?

 

As far as I can tell, the only way R401 and R402 can be blown is for IC401 and IC402 to be damaged.

To be on the safe side, remove IC401 and set aside.
Solder 8-pin socket and insert new RC4558P.

 

I finally got to do something here.

I have done some cleaning under the board, and I have now installed:
I actually got hold of some Sn/Pb solder it is a little better to use, i agree.

New IC402
Q401
Q405
new R506
resoldered R505
Soldered in socket and inserted new IC401 (RC4558P)


Some overview pictures of current situation

 

R517 looks discoloured or is that just the lighting in the photograph?

Install new
Q425, 2SA1123
Q427, 2SC3944 power transistor
Q429, 2SA1535 power transistor

Q402, 2SA1123
Q406, 2SC2631
Q408, 2SA1123

 

R517 looks discoloured or is that just the lighting in the photograph?
Install new
Q425, 2SA1123
Q427, 2SC3944 power transistor
Q429, 2SA1535 power transistor

Q402, 2SA1123
Q406, 2SC2631
Q408, 2SA1123

Yes, R517 is discoloured, because of R513 next to it has burned up twice or more.. hehe.

But i got curious and measured it.
Both R517 and R515 next to it, measures open circuit..

I checked two other similar resistors on the other channel, (R566, R568) just to check that my meter was ok.
And they measure the correct resistance, so my meter was ok.


Then i installed:

new Q425
new Q427
new Q429

original measured ok Q402
new Q406
new Q408


Just some overview pictures of current situation again: